linux-kernel - Re: [RFC] Should we create a raw input interface for IR's ? - Was: Re: [PATCH 1/3 v2] lirc core device driver infrastructure

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Message-ID: <4B1E5FAF.40201@redhat.com>
Date:	Tue, 08 Dec 2009 12:16:15 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Jon Smirl <jonsmirl@...il.com>
CC:	Andy Walls <awalls@...ix.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jarod Wilson <jarod@...sonet.com>,
	Krzysztof Halasa <khc@...waw.pl>,
	Christoph Bartelmus <lirc@...telmus.de>, j@...nau.net,
	jarod@...hat.com, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	superm1@...ntu.com
Subject: Re: [RFC] Should we create a raw input interface for IR's ? - Was:
 	Re: [PATCH 1/3 v2] lirc core device driver infrastructure

Jon Smirl wrote:
> On Tue, Dec 8, 2009 at 8:40 AM, Mauro Carvalho Chehab
> <mchehab@...hat.com> wrote:
>> Jon Smirl wrote:
>>> On Tue, Dec 8, 2009 at 7:35 AM, Andy Walls <awalls@...ix.net> wrote:
>>>> On Mon, 2009-12-07 at 20:22 -0800, Dmitry Torokhov wrote:
>>>>> On Mon, Dec 07, 2009 at 09:42:22PM -0500, Andy Walls wrote:
>>>>>> So I'll whip up an RC-6 Mode 6A decoder for cx23885-input.c before the
>>>>>> end of the month.
>>>>>>
>>>>>> I can setup the CX2388[58] hardware to look for both RC-5 and RC-6 with
>>>>>> a common set of parameters, so I may be able to set up the decoders to
>>>>>> handle decoding from two different remote types at once.  The HVR boards
>>>>>> can ship with either type of remote AFAIK.
>>>>>>
>>>>>> I wonder if I can flip the keytables on the fly or if I have to create
>>>>>> two different input devices?
>>>>>>
>>>>> Can you distinguish between the 2 remotes (not receivers)?
>>>> Yes.  RC-6 and RC-5 are different enough to distinguish between the two.
>>>> (Honestly I could pile on more protocols that have similar pulse time
>>>> periods, but that's complexity for no good reason and I don't know of a
>>>> vendor that bundles 3 types of remotes per TV card.)
>>>>
>>>>
>>>>>  Like I said,
>>>>> I think the preferred way is to represent every remote that can be
>>>>> distinguished from each other as a separate input device.
>>>> OK.  With RC-5, NEC, and RC-6 at least there is also an address or
>>>> system byte or word to distingish different remotes.  However creating
>>>> multiple input devices on the fly for detected remotes would be madness
>>>> - especially with a decoding error in the address bits.
>>> I agree that creating devices on the fly has problems. Another
>>> solution is to create one device for each map that is loaded. There
>>> would be a couple built-in maps for bundled remotes - each would
>>> create a device. Then the user could load more maps with each map
>>> creating a device.
>> No, please. We currently have already 89 different keymaps in-kernel. Creating
>> 89 different interfaces per IR receiver is not useful at all.
>>
>> IMO, the interfaces should be created as the keymaps are associated
>> to an specific IR receiver.
> 
> Each IR receiver device driver would have a built-in keymap for the
> remote bundled with it. When you load the driver it will poke the
> input system and install the map. Any additional keymaps would get
> loaded from user space. You would load one keymap per input device.
> 
> You might have 89 maps in the kernel with each map being built into
> the device driver for those 89 IR receivers. But you'll only own one
> or two of those devices so only one or two of the 89 maps will load.
> Building the map for the bundled receiver into the device driver is an
> important part of achieving "just works".
> 
> I suspect we'll have a 1,000 maps defined after ten years, most of
> these maps will be loaded from user space. But you'll only have two or
> three loaded at any one time into your kernel. You need one map per
> input device created. These maps are tiny, less than 1KB.
> 
> Having all of these maps is the price of allowing everyone to use any
> more that they please. If you force the use of universal remotes most
> of the maps can be eliminated.

Makes sense. Yet, I would add an option at Kbuild to create a module or not
with the bundled IR keymaps.

So, it should be possible to have all of them completely on userspace or
having them at kernelspace.

Cheers,
Mauro.
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